JP2002060978A - Steel having metallic coating and excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide steel excellent in corrosion resistance and suitable to uses for building materials of construction, automobiles, vessels or the like used at the outdoors. SOLUTION: This steel having a metallic coating and excellent in corrosion resistance has an alloy layer containing, by mass, >=5% Zn, 1 to 50% Al and 0.1 to 20% Mg, and the balance Fe with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel having a metal coating and excellent in corrosion resistance, and more particularly to a steel excellent in corrosion resistance suitable for use in outdoor construction materials, automobiles, ships and the like. .

[0002]

2. Description of the Related Art Conventionally, steel used for civil engineering construction materials, automobiles, ships, etc. is used by applying a metal coating such as zinc plating, aluminum plating, or zinc spraying to the surface of the steel in order to suppress corrosion. In many cases. in recent years,
In order to further extend the life of steel materials, for example, Zn-Cr-Al-based hot-dip galvanizing proposed in JP-A-5-222502, and Al-Si proposed in JP-A-11-29735 are disclosed. -Steel materials, such as Mg-Zn-plated steel sheets, have been proposed in which an alloying element is added to conventional zinc plating or aluminum plating and a metal coating layer having improved corrosion resistance is formed on the surface of the steel.

[0003]

In a steel material having a metal coating as represented by the above-mentioned plated steel sheet, an alloy layer is formed at the interface between the steel and the metal coating layer in the manufacturing process, but the corrosion resistance is not good for the surface. In most cases, the development is focused on only the metal coating layer formed on the metal coating, and in fact, it is attempted to improve the corrosion resistance by adding various alloying elements into the metal coating. However, in response to the recent demand for longer life of steel materials, it is necessary to further improve corrosion resistance.

[0004]

Accordingly, the present inventors have
Means for solving the above problems have been studied from various viewpoints. As a result, in a steel material having a metal coating, it is possible to further improve the corrosion resistance of a steel material having a conventional metal coating by providing an alloy layer having an appropriate component system between the metal coating and the steel material. I found it. The details are as follows. (1) In a steel material having a metal coating, Zn: 5% or more, Al: 1 to 50 by mass% between the metal coating and the steel material.
%, Mg: 0.1 to 20%, the balance being an alloy layer composed of Fe and irreversible impurities, and having excellent corrosion resistance having a metal coating. (2) The alloy layer further contains Ni: 0.01 to 2% by mass.
0%, Cr: 0.01 to 10%, Si: 0.01 to 10
%, Ca: 0.01 to 5%, Be: 0.01 to 5%, S
r: 0.01 to 5%, Ba: 0.01 to 5%, Mn:
The steel with excellent corrosion resistance having a metal coating according to claim 1, comprising one or more of 0.01 to 5%. (3) The steel having a metal coating and excellent in corrosion resistance according to claim 1 or 2, wherein the alloy layer has a thickness of 0.1 to 50 µm. (4) The steel excellent in corrosion resistance having a metal coating according to any one of claims 1 to 3, wherein the metal coating is Zn and / or a metal mainly composed of Zn. (5) The steel excellent in corrosion resistance having a metal coating according to any one of claims 1 to 3, wherein the metal coating is Al and / or a metal mainly composed of Al. (6) a chemical conversion treatment layer on the metal coating layer, and / or
A steel having a metal coating according to any one of claims 1 to 5 and having excellent corrosion resistance, which has a resin layer.

[0005]

Embodiments of the present invention will be described below in detail. The original plate used in the present invention may be any steel material such as a commonly used cold-rolled steel material, a cold-rolled steel material subjected to annealing and tempering, a hot-rolled steel material, a cast material, and the like. First, the reasons for limiting the components in the alloy layer will be described. Zn; Zn improves the corrosion resistance of steel by a sacrificial corrosion protection effect. This effect appears when the content of Zn in the alloy layer is 5% by mass, and the effect increases as the Zn content increases.
The upper limit of the Zn content is not particularly limited. However, when Zn exceeds 80% by mass, the corrosion resistance is saturated. For this reason, the content of Zn in the alloy layer in the present invention is 5% by mass or more,
Desirably, it is specified in the range of 5 to 80% by mass.

Al: Al is an element effective for improving the corrosion resistance of the galvanized layer. This effect appears from an Al content of 1% by mass in the alloy layer, and the effect increases as the Al content increases. However, when the content of Al exceeds 50% by mass, the temperature of the galvanizing bath becomes high, and undesired results such as an increase in dross generation and an increase in manufacturing cost are produced. Therefore, the content of Al in the alloy layer in the present invention is 1 to 50.
It is specified in the range of mass%. The preferred range is 5 to 40% by mass.
It is.

Mg: Mg improves the corrosion resistance of the alloy layer. This effect appears when the content of Mg in the alloy layer is 0.1% by mass, and the effect increases as the content increases. However, if Mg exceeds 20% by mass, the corrosion resistance is saturated, and the hardness of the alloy layer is increased, so that problems such as cracking of the alloy layer during processing are likely to occur. For this reason, the content of Mg in the alloy layer in the present invention is specified in the range of 0.1 to 20% by mass. A preferred range is 1 to 10%.

[0008] The above components and Fe
Steel having an alloy layer composed of irreversible impurities has excellent corrosion resistance. Specifically, for example, if the metal coating layer is Zn
In the case of, the corrosion resistance of the scratched portion of the steel plate is improved by the sacrificial corrosion prevention effect of Zn, but the corrosion of the steel plate starts after the disappearance of Zn. On the other hand, when an alloy layer is provided between the metal coating layer of Zn and the steel material, the corrosion resistance of the scratched part of the steel sheet is improved by the sacrificial corrosion prevention effect of Zn, and even after the disappearance of Zn, the above alloy having excellent corrosion resistance The layer can suppress corrosion of the steel sheet.

In the present invention, the following elements can be further contained in the alloy layer if necessary, in which case the corrosion resistance of the steel is further improved. Ni: Ni improves the corrosion resistance of the alloy layer. This effect is caused by the Ni in the alloy layer.
Appears from 0.01% by mass, and the effect increases as the content increases. However, when Ni exceeds 20% by mass, the corrosion resistance is saturated. For this reason, the content of Ni in the alloy layer in the present invention is defined in the range of 0.01 to 20% by mass. A preferred range is from 0.5 to 10%.

Cr: Cr has the effect of improving the corrosion resistance of the alloy layer. This effect is due to the Cr content in the alloy layer,
It appears from 0.01% by mass, and the effect increases as the amount increases. However, when the content of Cr exceeds 10% by mass, not only the cost is increased unnecessarily, but also the problem that the hardness of the alloy layer is increased and the alloy layer is cracked at the time of processing is liable to occur. For this reason,
In the present invention, the content of Cr in the alloy layer is from 0.01 to 1
It is specified in the range of 0% by mass. The preferred range is 0.1-5%
It is.

Si: Si has an effect of improving corrosion resistance. This effect is obtained when the metal coating layer is made of Zn or a metal mainly composed of Zn, and the content of Si in the alloy layer is set to 0.1.
It appears from 01% by mass, and the effect increases as the amount increases. However, if Si exceeds 10% by mass, the corrosion resistance is saturated, and even if it is further increased, the cost will simply increase unnecessarily. Therefore, when the metal coating layer is made of Zn or a metal mainly composed of Zn, the content of Si in the alloy layer in the present invention is defined in the range of 0.01% by mass to 10% by mass. The metal coating layer is made of Al or A
In the case where the metal is mainly composed of l, this effect appears when the content of Si in the alloy layer is about 0.1% by mass, and the effect increases as the content increases. However, Si is 10% by mass.
Above this point, the corrosion resistance saturates, and any further increase will merely increase the cost unnecessarily. For this reason,
When the metal coating layer is made of Al or a metal mainly composed of Al, the content of Si in the alloy layer in the present invention is 0.1%.
It is specified in the range of 10% by mass to 10% by mass.

Ca: Ca has the effect of improving corrosion resistance. This effect appears when the content of Ca in the alloy layer is 0.01% by mass, and the effect increases as the content increases. However, when Ca exceeds 5% by mass, the corrosion resistance is saturated, which not only increases the cost unnecessarily, but also increases the hardness of the alloy layer and easily causes problems such as cracking during processing. For this reason, the content of Ca in the alloy layer in the present invention is 0.01
It is specified in the range of ５5% by mass.

Be: Be improves the corrosion resistance of the alloy layer. This effect appears when the content of Be in the alloy layer is 0.01% by mass, and the effect increases as the content increases. However, if Be exceeds 5% by mass, the corrosion resistance is saturated, which not only increases the cost unnecessarily, but also increases the hardness of the alloy layer and easily causes problems such as cracking during processing. For this reason, the content of Be in the alloy layer in the present invention is set to 0.01.
It is specified in the range of ５5% by mass.

Sr: Sr improves the corrosion resistance of the alloy layer. This effect appears when the content of Sr in the alloy layer is 0.01% by mass, and the effect increases as the content increases. However, when Sr exceeds 5% by mass, the corrosion resistance is saturated, not only unnecessarily increasing the cost but also increasing the hardness of the alloy layer and easily causing problems such as cracking during processing. For this reason, the content of Sr in the alloy layer in the present invention is set to 0.01%.
It is specified in the range of ５5% by mass.

Ba; Ba improves corrosion resistance. This effect appears when the content of Ba in the alloy layer is 0.01% by mass, and the effect increases as the content increases. However, when Ba exceeds 5% by mass, the corrosion resistance is saturated. For this reason, the content of Sr in the alloy layer in the present invention is specified in the range of 0.01 to 5% by mass.

Mn: Mn has an effect of improving corrosion resistance. This effect appears when the content of Mn in the alloy layer is 0.01% by mass, and the effect increases as the content increases. However, when Mn exceeds 5% by mass, the corrosion resistance saturates, and even if it is further increased, the cost simply increases unnecessarily. For this reason, the content of Mn in the alloy layer in the present invention is specified in the range of 0.01 to 5% by mass. The above-mentioned components in the alloy layer alone improve the corrosion resistance, but it is desirable to contain two or more of them, and the corrosion resistance is further improved.

The thickness of the alloy layer of the present invention is 0.1 to 50 μm.
m. The reason is that if the thickness of the alloy layer is less than 0.1 μm, the corrosion resistance for a long period is insufficient, and if it exceeds 50 μm, the corrosion resistance is saturated and the cost is simply increased unnecessarily. The zinc-based metal that forms the metal coating is a metal in which the component occupying the largest amount of the metal is zinc, that is, a zinc-based alloy, and aluminum, magnesium, and other alloy components generally contained in the zinc-based alloy and May contain impurities. The metal coating made of a zinc-based alloy has the effect of improving the corrosion resistance of steel by its sacrificial corrosion protection action. The metal mainly composed of aluminum is a metal in which the component occupying the largest amount of the metal is aluminum, that is, an aluminum-based alloy. May be included. The metal coating made of an aluminum-based alloy has an effect of further improving the corrosion resistance of steel due to its excellent corrosion resistance.

Next, the manufacturing conditions will be described. As a method of forming the alloy layer between the metal coating and the steel material in the present invention, any method can be used as long as the metal coating and the alloy layer can be sufficiently adhered to the steel material. For example, a metal coating containing an element contained in the alloy layer of the steel material of the present invention may be formed on the steel material by hot dipping, or electroplating, molten salt electroplating, vacuum evaporation, sputtering, ion plating, or the like. it can. Also,
If necessary, after forming a metal coating layer on the steel material containing the elements contained in the alloy layer of the steel material of the present invention by hot-dip plating, or electroplating, molten salt electrolytic plating, vacuum evaporation, sputtering, ion plating, etc. By performing heat treatment or the like, a metal-coated steel material having the alloy layer of the present invention can also be obtained.

Further, a chemical conversion treatment layer, a resin layer and the like can be further provided on the metal coating layer of the present invention. By having a chemical conversion treatment layer, the effect of extending the life of steel can be expected. Examples of the chemical conversion treatment layer include generally known chromate layers and phosphate treatment layers. As the resin layer, generally known ones can be used, and examples thereof include those mainly composed of an epoxy resin, a polyester resin, a urethane resin, an acrylic resin, a melamine resin and the like. These resins may be used by mixing several kinds as necessary. In addition, this resin layer is made of zinc phosphate, iron phosphate, calcium molybdate, aluminum molybdate, vanadium oxide, strontium chromate,
Rust preventing pigments such as zinc chromate and silica may be included. As a method for forming the resin layer, any method can be used as long as it can sufficiently adhere to steel. For example, brush coating, dip coating, bar coating, spray coating, electrodeposition coating, electrostatic coating, roll coater coating, die coater,
Curtain flow coating, roller curtain coating and the like can be mentioned. As described above, the steel having excellent corrosion resistance having the metal coating of the present invention can be used as a steel material used for civil engineering construction materials, automobiles, ships, and the like.

[0020]

EXAMPLES (Example 1) A plated steel sheet having the composition shown in Table 1 was manufactured and its corrosion resistance was examined. The concentration of each element in the alloy layer was adjusted to a predetermined concentration by adjusting the cooling rate after plating in the range of 15 to 100 ° C./sec. The manufacturing conditions are as follows. The plating bath temperature is 450
It adjusted within the range of ５550 ° C.・ Plating base plate: 5% Cr steel (thickness: 0.8 mm) ・ Base plate heating rate: 30 ° C./sec ・ Maximum heating temperature: 800 ° C. ・ Plating bath temperature: 450-550 ° C. ・ Immersion time: 3 seconds Corrosion resistance Was subjected to SST (salt spray test according to JIS2371), and evaluated according to the following criteria based on the red rust occurrence rate after 1000 hours. ◎: Red rust occurrence rate of 0 to less than 10% ○: Red rust occurrence rate of less than 10 to 30% △: Red rust occurrence rate of 30 to less than 50% ×: Red rust occurrence rate of 50% or more Thereafter, a tape test was performed and evaluated according to the following criteria. ◎: no peeling ○: small peeling Δ: large peeling ×: full peeling

[0021]

[Table 1] As shown in Table 1, the steel of the present invention (No. 3 to 6, 9 to 12,
15-17, 19-21, 23-26, 29-32, 3
5-39, 41, 42, 44, 45, 47, 48, 51
~ 60) are comparative examples (No. 1, 2, 7, 8, 13, 1).
4, 18, 22, 27, 28, 33, 34, 40, 4
3, 46, 49, 50), thereby improving the corrosion resistance and adhesion.

Example 2 A coated steel sheet having the composition shown in Table 2 was manufactured and its corrosion resistance was examined. The concentration of each element in the alloy layer is
A predetermined concentration was obtained by adjusting the cooling rate after plating in the range of 15 to 100 ° C./sec. The manufacturing conditions are as follows. The plating bath temperature should be 50 in accordance with the plating component concentration.
The temperature was adjusted in the range of 0 to 650 ° C.・ Plating original sheet: 5% Cr steel (thickness: 0.8 mm) ・ Base sheet heating rate: 30 ° C./sec ・ Maximum heating temperature: 800 ° C. ・ Plating bath temperature: 500-650 ° C. ・ Immersion time: 3 seconds Corrosion resistance and The method of evaluating the adhesion is the same as in Example 1.

[0023]

[Table 2] As shown in Table 2, the steel of the present invention (No. 63 to 66, 69 to
72, 75-77, 79-81, 83-86, 89-9
2, 95-99, 101, 102, 104, 105, 1
07, 108, 111 to 120) are comparative examples (No. 6).
1, 62, 67, 68, 73, 74, 78, 82, 8
7, 88, 93, 94, 100, 103, 106, 10
9, 110), the corrosion resistance and adhesion are improved.

[0024]

As described above, the steel of the present invention makes it possible to provide steel having excellent corrosion resistance in severely corrosive environments such as civil engineering materials, automobiles and ships.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C23C 28/00 C23C 28/00 A C // C22C 21/06 C22C 21/06 21/10 21/10 (72) Invention Person Kenji Kato 20-1 Shintomi, Futtsu-shi, Chiba F-term in the Technology Development Division of Nippon Steel Corporation 4K044 AA02 AB02 BA10 BA15 BA17 BA21 BB01 BB03 BB04 BC02 BC05 CA11 CA13 CA16 CA18 CA62

Claims (6)

[Claims] 1. A steel material having a metal coating, wherein Zn: 5% or more, Al: 1 to 50%, Mg: 0.1 to 20% by mass% between the metal coating and the steel material, with the balance being Fe A steel having a metal coating characterized by having an alloy layer composed of irreversible impurities and having excellent corrosion resistance. 2. The alloy layer further includes: Ni: 0.01 to 20% Cr: 0.01 to 10% Si: 0.01 to 10% Ca: 0.01 to 5% Be: 0.1 to 20% by mass. 2. The metal according to claim 1, wherein the metal comprises one or more of Sr: 0.01 to 5%, Ba: 0.01 to 5%, and Mn: 0.01 to 5%. Steel with coating and excellent corrosion resistance. 3. The steel with excellent corrosion resistance having a metal coating according to claim 1, wherein the thickness of the alloy layer is 0.1 to 50 μm. 4. The steel having excellent corrosion resistance according to claim 1, wherein the metal coating is Zn and / or a metal mainly composed of Zn. 5. The steel with excellent corrosion resistance according to claim 1, wherein the metal coating is Al and / or a metal mainly composed of Al. 6. A chemical conversion treatment layer and / or a resin layer on the metal coating.
5. A steel excellent in corrosion resistance having the metal coating according to any one of 5.